For reference I just wanted to add a correction to my earlier assumption re the patterns in my Welsh stone, Having spoken to my Geology mate about this he tells me theyre probably not from the original sedimentary deposition but to quote him.
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The texture you're seeing I think is crenulations. They are
microfolds formed when the rock was deformed/metamorphosed.
I suspect that new minerals that grow during metamorphism
may also orientate in response to the stress direction.
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A small point maybe of interest to some.